The present Applicant has previously disclosed a printing system and process wherein images made up of inks having an aqueous carrier are jetted onto a recirculating intermediate transfer member that transports them to an impression station where they are transferred to the desired printing substrate (e.g., paper, cardboard, plastic films etc.). As against inkjet printers, that deposit ink directly onto the printing substrate, such systems allow the distance between the surface of the intermediate transfer member and the inkjet print head to be maintained constant and reduces wetting of the substrate, as the inks may be dried while being transported by the intermediate transfer member before they are transferred to the substrate. Consequently, the final image quality on the substrate is less affected by the physical properties of the substrate and benefits from various other advantages as a result of the image remaining above the substrate surface. More details of such a system are disclosed in WO2013/132418, filed on Mar. 5, 2013 and incorporated herein by reference.
The present disclosure is concerned with an apparatus for assisting with the initial installation of the intermediate transfer member in such a printing system and with its replacement when the need arises without having to separate the various components of the printing system.
At the image forming station, the intermediate transfer member in such a printing system needs to pass through a narrow gap between the print heads and its own support and drive system, and it needs to be maintained both taut and at a fixed distance from the print heads. To achieve this, WO 2013/132418 describes in FIG. 11 how formations may be provided along the lateral edges of the intermediate transfer member that are received in guide channels having, for instance, a C-shaped cross section that is shown in FIG. 12 of the latter publication. The formations may be the teeth of two zip fastener halves, or any other type of “beads” that can properly move in the guide channels, that are attached to the respective lateral edges of the intermediate transfer member and their engagement in the guide channels serves both to constrain the path followed by the intermediate transfer member and to maintain it under lateral tension.
The intermediate transfer member is seamed once installed and starts life as a long strip, also termed a blanket in practice, but the latter term will not be used herein as it also common to refer to the installed intermediate transfer member as a blanket. The strip needs to be threaded through the various stations of the printing systems and, after it has been threaded around its entire path, its ends strip can be cut to the correct length, if necessary, and joined to one another to form a continuous loop. The ends of the strip can be attached to one another by soldering, gluing, taping (e.g., using Kapton® tape, RTV liquid adhesives or PTFE thermoplastic adhesives with a connective strip overlapping both edges of the strip), or any other method commonly known. Any method of joining the ends of the blanket strip to form an intermediate transfer member may cause a discontinuity, referred to herein as a seam.
The seam can be of different types. In particular, the edges may overlap one another or a patch may be applied to overlie the two ends. In either case, the seam may be subsequently processed, such as my grinding, to reduce its thickness.
To feed the strip into the printing system, it was proposed by the present Applicant in WO2013/136220 to provide entry points in the guide channels and to mount an external threading mechanism, shown in FIGS. 9 and 10 of the latter publication, for gripping the formations on the lateral edges of the strip and advancing its two lateral edges at the same rate into their respective guides. However, even with the aid of such a threading mechanism, it was found that the intermediate transfer member was difficult to install on account of buckling on meeting resistance or an obstruction.
It was also proposed in WO2013/136220 (see FIG. 13) to provide a loop of cable permanently housed in one or both of the tracks. The aim was to anchor the leading end of the replacement belt to the cable then to use the cable to feed the strip through the various tracks. During normal use, the cable(s) would remain stationary in the track(s) and only be rotated during installation of a new intermediate transfer member.
The use of cable loops was not found satisfactory and the present disclosure therefore aims to simplify the task of installing and replacing an intermediate transfer member in an indirect printing system.